1. Technical Field
Exemplary aspects of the present invention generally relate to a moving device and an image forming apparatus including the moving device.
2. Related Art
Conventionally, known image forming apparatuses employ an optical writing head including a plurality of light emitting elements arranged in an axial direction of a photosensitive member on which a latent image is formed.
Image forming apparatuses of this kind include a type equipped with a moving device that moves the optical writing head between an engaged position at which the optical writing head writes the latent image on the surface of the photosensitive member and a retracted position. FIG. 9 is a schematic diagram illustrating such a moving device 250, located near a writing head 231. FIG. 10 is a top view of the moving device 250 shown in FIG. 9.
The writing head 231 shown in FIG. 9 is held by a holder 233. The holder 233 includes a guide rod 236 that penetrates through a frame 240 of the image forming apparatus. A spring seat 242 is provided to an end of the guide rod 236, and a compression spring 243 is disposed between the spring seat 242 and the frame 240.
As illustrated in FIGS. 9 and 10, the moving device 250 includes a pair of pressing levers 245, a lever 248, an arm 251, a rib 262, and so forth. The pair of pressing levers 245 is fixed to a shaft 246 at a predetermined interval. The shaft 246 is rotatably supported by a pair of brackets 247 disposed on the upper surface of the frame 240. The lever 248 is fixed substantially at the center of the shaft 246. One end of a wire 249 is connected to the lever 248. The other end of the wire 249 is fixed to an end of the arm 251, which is swingably attached to the front side (the lower side in FIG. 10) of the frame 240. The other end of the arm 251 is biased by a coil spring 249B in the direction indicated by an arrow D. The rib 262 is disposed on the inner surface of an openably closable front cover 260. The front cover 260 is attached to the front side of the frame by a hinge 261.
With the front cover 260 closed, the rib 262 presses the end of the arm 251 in the direction indicated by an arrow A while the pair of the pressing levers 245 presses the spring seat 242 against the compression spring 243, thereby pressing the holder 233 against a photosensitive member 211. With this configuration, the writing head 231 is positioned at the engaged position.
Upon replacement of the photosensitive drum 211, the front cover 260 is opened, moving the rib 262 in the opposite direction of the direction of arrow A in FIG. 10. Subsequently, the coil spring 249B and the compression spring 243 cause the arm 251 to rotate in the direction of arrow B in FIG. 10, and the wire 249 moves in the direction of arrow C. As the wire 249 moves in the direction of arrow C, the shaft 246 rotates in the direction of arrow E, thereby rotating the pressing levers 245 in the direction of arrow G in FIG. 9. With this configuration, the holder 233 is moved in the direction of arrow H by the compression spring 243, thereby moving the writing head 231 from the engaged position to a retracted position at which the writing head 231 is separated from the photosensitive member 211.
As the front cover 260 is completely opened, the pressing lever 245 is separated from the spring seat 242 as indicated by a broken line in FIG. 9. As a result, the compression spring 243 obtains its free length, thereby moving the writing head 231 with the holder 233 to the retracted position indicated by the broken line.
In the configuration described above, when the writing head 231 is at the retracted position, the pressing levers 245 are biased by the coil spring 249B and the compression spring 243 in the direction corresponding to the direction in which the writing head 231 is moved from the engaged position to the retracted position. Accordingly, even when the image forming apparatus receives some stress upon replacement of the photosensitive member, a developing device, and so forth, the writing head 231 does not easily move from the retracted position to the engaged position.
The rib 262 restricts rotation of the arm 251 to position the writing head 231 at the engaged position. Although advantageous, because the rib 262 is disposed on the front cover 260, which is opened and closed relative to the frame of the image forming apparatus, the restriction position of the arm 251 varies, and it is difficult to reliably position the writing head 231 at the engaged position with precision. As a result, a high-resolution latent image is not formed on the surface of the photosensitive member.